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ENN Original news: Landslides and Earthquakes linked



From: Roger Greenway, ENN
Published January 6, 2014 08:21 AM

Landslides and Earthquakes linked

Earthquakes can cause landslides, and often do. But can a landslide cause an earthquake? Looks like they can, if they are big enough!

Last year’s gigantic landslide at a Utah copper mine probably was the biggest nonvolcanic slide in North America’s modern history, and included two rock avalanches that happened 90 minutes apart and surprisingly triggered 16 small earthquakes, University of Utah scientists discovered.

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The landslide — which moved at an average of almost 70 mph and reached estimated speeds of at least 100 mph — left a deposit so large it “would cover New York’s Central Park with about 20 meters (66 feet) of debris,” the researchers report in the January 2014 cover study in the Geological Society of America magazine GSA Today.

While earthquakes regularly trigger landslides, the gigantic landslide the night of April 10, 2013, is the first known to have triggered quakes. The slide occurred in the form of two huge rock avalanches at 9:30 p.m. and 11:05 p.m. MDT at Rio Tinto-Kennecott Utah Copper’s open-pit Bingham Canyon Mine, 20 miles southwest of downtown Salt Lake City. Each rock avalanche lasted about 90 seconds.

While the slides were not quakes, they were measured by seismic scales as having magnitudes up to 5.1 and 4.9, respectively. The subsequent real quakes were smaller.

Kennecott officials closely monitor movements in the 107-year-old mine — which produces 25 percent of the copper used in the United States — and they recognized signs of increasing instability in the months before the slide, closing and removing a visitor center on the south edge of the 2.8-mile-wide, 3,182-foot-deep open pit, which the company claims is the world's largest manmade excavation.

Photo Credit: Kennecott Utah Copper

Read more at University of Utah.

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